1.

Structure of the Lesson

Class
Class

1. intro – Overview of the lesson

Intro
Intro
2. Learning objective – present learning objective of the lesson
3. Table of Content – structure of the topics and subtopics in
the lesson

Study
Study
4. Lecture (75-90 minutes)
– present the lecture in detailed topics that covers all the
learning objectives of the lesson.
Assessment
Assessment - each topics should be divided into subtopics
(5-15 min in length is recommended)
- if a subtopic goes over 15 minutes divide the subtopic into
series of subtopics.
Review
Review

Class
Class end
end
 Circuit theory and Labo-
Course
ratory
Lesson # Lesson 1
Introduction-Diode appli-
Title
cations
SME Dr. Nguyen Vu Thang
 Learning Objectives Table of Content
At the end of this lecture, you •Introduction
should be able to: •Diode overview
•Understand the configuration, •Rectifier
operation and measurement of •Clipper
different applications of diode. •Clamper
•The applications are: rectifier, •Zener diode
clippers, clampers, Zener diodes •Voltage multiplication
and voltage multiplication
 Content
•Introduction
•Diode overview
•Rectifier
•Clipper
•Clamper
•Zener diode
•Voltage multiplication
 Objectives
 On completion of this course, the student will
understand
◦ Able to explain, describe, and use physics-based device and
circuit models for semiconductor devices
◦ Able to choose appropriate BJT and FET configuration
◦ Able to choose and calculate appropriate biasing
◦ Understand effect of source, load resistance; power, frequency
limitation
◦ Understand the advantages and method of analysis of
feedback
◦ Able to analyze and design electronic circuits
◦ Able to Identify the design issues, and develop solutions
 Grading

Activities Percentage
Homework 30%
Midterm exam 30%
Final exam 40%
Total 100%
 Reference books
 Text book:
◦ Robert Boylestad, Louis Nashelsky, Electronic Devices and
Circuit Theory, 2002
 Reference books:
◦ Richard C. Jaeger, Microelectronic Circuits Design, 2003
◦ Microelectronic Circuits; Fifth Edition by Sedra/Smith
◦ Microelectronic circuits, 5th edition, Behzad Razavi
 Websites:
◦ http://www.discovercircuits.com/list.htm
◦ http://www.epanorama.net/links/basics.html
◦ http://www.datasheetcatalog.com/
 Content
•Introduction
•Diode overview
•Rectifier
•Clipper
•Clamper
•Zener diode
•Voltage multiplication
 Diode overview

It is a 2-terminal device

9
 Diode overview
Ideally it conducts current in only one direction

and acts like an open in the opposite direction

10
 Characteristics of an ideal diode:
Conduction Region

In the conduction region (the vertical blue line), ideally

• the voltage across the diode is 0V,
• the current is ,
• the forward resistance (RF) is defined as RF = VF/IF= 0
• the diode acts like a short.

11
 Characteristics of an ideal diode:
Non-Conduction Region

In the non-conduction region (the horizontal blue line), ideally

• all of the voltage is across the diode,
• the current is 0A,
• the reverse resistance (RR) is defined as RR = VR/IR, = ∞
• the diode acts like open.

12
 Actual Diode Characteristics

Note the regions for No Bias, Reverse Bias, and Forward

Bias conditions.
13
Practical Diode
Silicon Germanium
Higher *PIV ( 1000V) Lower PIV ( 400V)
Higher current rating Lower current rating
Wider temperature Narrow temperature
range (up to 2000C) range (lower than 1000C)
Higher forward-bias Lower forward-bias
voltage (0.7V) voltage (0.3V)
* PIV = peak inverse voltage

14
Comparison of Si and Ge diodes

15
Diode specification sheets

16
Diode examples

17
Diode examples

18
 Content
•Introduction
•Diode overview
•Rectifier
•Clipper
•Clamper
•Zener diode
•Voltage multiplication
 Rectifier circuits
• Types
– Half-wave
– Full-wave
– Full-wave bridge
– With capacitor
 Half-wave rectifier

• Vi(t)>0 => D on
• Vi(t)<0 => D off
 Half-wave rectifier

• Effect of VT
 Half-wave rectifier

• Example:
– (a) Sketch the output vo and determine the dc level of the
output for the network of figure above
– (b) Repeat part (a) if the ideal diode is replaced by a silicon
diode.
– (c) Repeat parts (a) and (b) if Vm is increased to 200 V and
compare solutions
 Half-wave rectifier

• A. For ideal diode:

– Vdc = -0.318Vm = -0.318(20 V) = -6.36 V

• B. For Si diode:
– Vdc = -0.318(Vm - 0.7 V) = -0.318(19.3 V) = -6.14 V

• C. for ideal diode:

– Vdc =-0.318Vm = -0.318(200 V) = -63.6 V

• For Si diode:
– Vdc =-0.318(Vm -VT) = -0.318(200 V-0.7 V) = -63.38 V
 Full-wave rectifier

• Center-taped transformer
• Bridge network
 Full-wave rectifier
center-taped transformer

Circuit and input

Positive region
Vi>0 => D1 on, D2 off

Negative region
Vi<0 => D1 off, D2 on
Full-wave rectifier
Bridge rectifier

Circuit and input

 Full-wave rectifier
Bridge rectifier

 Positive half:
 V >0 => D2, D4 on; D1, D3 off
i
 Full-wave rectifier
Bridge rectifier

 Negative half:
 V <0 => D2, D4 off; D1, D3 on
i
 Full-wave rectifier
Bridge rectifier

 Waveform of Full wave

 Ideal diode: V = 0.636V
dc m
 Silicon diode: Vdc = 0.636(Vm - 2VT)
Full-wave rectifier
Rectifier with capacitor
 Content
•Introduction
•Diode overview
•Rectifier
•Clipper
•Clamper
•Zener diode
•Voltage multiplication
 Clippers
- Is a diode network that have the ability to “clip”
off a portion on the input signal without distorting
the remaining part of the alternating waveform.
- Used to eliminate amplitude noise or to fabricate
new waveforms from an existing signal.
 Clipper

Series: Parallel:
•The series configuration is •The series configuration is
defined as one where the diode is defined as one where the diode is
in series with the load. parallel with the load.
 Clipper

• Series:
– Vi>V => D on => Vo=Vi-V
– Vi<V => D off => Vo=0
 Clipper

• Example: determine output waveform for the

network above
 Clipper

Solution
 Clipper
Example:
• Repeat the previous example using for the
square wave input
 Clipper

• Parallel network
• The diode connection is in parallel
configuration with the output.
 Clipper

• Parallel:
– Vi>0 => D on => Vo=0
– Vi<0 => D off => Vo=Vi
 Clipper

• Example: determine Vo sketch the output

waveform for the above network
 Clipper
Solution

Negative region of vi

Positive region of vi
 Clipper

• Example: repeat the previous example using a

silicon diode
 Clipper

Vo
• Solution: 16
• Vi>3.3V => D on => Vo = Vi
3.3
• Vi<3.3V => D off => Vo = 3.3V 0 T/2 T
t

Output waveform
Clipper - summary

45
Clipper - summary

46
 Content
•Introduction
•Diode overview
•Rectifier
•Clipper
•Clamper
•Zener diode
•Voltage multiplication
 Clamper
• The clamping network is to “clamp” a signal to a different dc level.
• Often used in TV receivers as a dc restorer.
• The network consists of:
– a) Capacitor
– b) Diode
– c) Resistive element
– d) Independent dc supply (option)
• The magnitude of R and C must be chosen such that the time
constant ζ = RC is large enough to ensure that the voltage across
the capacitor does not discharge significantly during the interval the
diode is nonconducting.
• Assume in our analysis that all capacitor is fully charge and
discharge in 5 time constant.
 Clamper

• Network
Clamper
Operation:
• 0 → T/2: D on
=> RC time constant is small because of
the resistance of the diode
=> capacitor charge to V volts quickly
=> Vo = 0 V
• T/2 → T: D off
=> RC time constant > 5T >> T/2
=> can assume capacitor keep all charges
and voltage during this period => Vo = -2V
 Clamper

Total swing output signal = the

total swing input signal

51
Clamper

Example: Determine vo for the network above for

the input indicated

52
Clamper
Solution:
•F=1000 Hz => interval between levels =
0.5 ms
•0 → t1: D off => Vo = 10 V
•t1 →t2: D on => network will appear as Fig. 2
shown in Fig. 2
Vc = V + Vi = 25 V
Vo = 5V
•t2 →t3: D off => network will appear as
shown in Fig. 3 Fig. 3

Vo = Vc+Vi = 25 + 10 = 35 V
53
Clamper

Solution:
•Time Constance
ζ = RC = (100kΩ)(1 µF) = 0.1 s =100ms
•The total discharge time = 5ζ = 500 ms
=> the capacitor can hold the voltage during the interval
of 0.5 ms

54
Clamper

55
 Content
•Introduction
•Diode overview
•Rectifier
•Clipper
•Clamper
•Zener diode
•Voltage multiplication
Zener diode

• The zener diode is a special type of diodes that is

designed to work in the reverse breakdown region.
• Can operate in the forward bias region.
• Application: always reverse bias
– Reference voltage for DC power supply
 Zener diode simple application

• Example: Fixed DC voltage is applied in the network

above. Analyze the operation of the network.
 Zener diode simple application

Solution:
• Determine the state of the Zener diode by removing it from
the network:
V = VL = RLVi/(R+RL)
• If V > Vz => D on => Zener diode works as a DC source
• If V < Vz => D off => open circuit for Zener diode
 Zener diode simple application

Solution (continue):
• We have:
• IR=(Vin-Vz)/R;
• IL=Vz/RL;
• Pz=Iz*Vz<Pzmax
 Zener diode simple application

• Case 1: fixed Vin, variable RL

RLmax> RL >RLmin
RLmax=Vz/(IR-Izmax)
RLmin=RVz/(Vi-Vz)
 Zener diode simple application

• Case 2: fixed RL, variable Vin

RLmax> RL >RLmin
RLmax=Vz/(IR-Izmax)
RLmin=RVz/(Vi-Vz)
 Zener diode simple application

Example:
• Given the Zener diode network above
• a) Determine VL, VR, IZ, and PZ.
• b) Repeat with RL = 3kΩ
 Zener diode simple application

Solution: part a
• VZ = RLVi/(R+RL) = 8.73 V < 10 V
• => Zener diode is off
• VRL = 8.73 V
• IZ = 0 A
• PZ = 0 W
 Zener diode simple application

Solution (continue): part b

• VZ = RLVi/(R+RL) = 12 V > 10 V
• => Zener diode is on
• VRL = VZ = 10 V => VR = 6V
• IRL = 3.33 mA; IR = 6 mA; IZ = 2.67 mA
• PZ = IZVZ = 26.7 mW
 Zener diode simple application

Example:
• Given the network above
• a) Determine the range of RL and IL that will result in VRL
being maintained at 10 V.
• b) Determine the maximum wattage rating of the diode
 Zener diode application

AC regulator
 Zener diode application

Simple square generator

 Content
•Introduction
•Diode overview
•Rectifier
•Clipper
•Clamper
•Zener diode
•Voltage multiplication
 Voltage multiplier
• Voltage-multiplier circuits are employed to
maintain a relatively low transformer peak voltage
while stepping up the peak output voltage to two,
three, four, or more times the peak rectified
voltage
 Double voltage

• Positive phase: D1 on, D2 off, VC1=Vm

• Nagative phase: D1 off, D2 on, VC2=Vm+VC1=2Vm
 Multiple voltage

• Positive phase: D1 on, D2 off, VC1=Vm

• Negative phase: D1 off, D2 on, VC2=Vm+VC1=2Vm
 Real Diode applications
• Rectifier Circuits
–
Conversions of AC to DC for DC operated circuits
–
Battery Charging Circuits
• Simple Diode Circuits
–
Protective Circuits against Overcurrent
–
Polarity Reversal Currents caused by an inductive kick in
a relay circuit
• Zener Circuits
–
Overvoltage Protection
–
Setting Reference Voltages